Vascular endothelial cells play the improtant roles in regulation of the local blood flow by producing some vasoactive peptides such as endothelin (ET) -1 and calcitonin gene-related peptide (CGRP), and by releasing them into both vascular lumen and subendothelial layr. Our immunoelectron microscopy revealed that ET-1 and CGRP are synthesized and segregated in the rough endoplasmic reticulum-Golgi system, stored in part in Weibel-Palade (WP) bodies in endothelial cells of the transverse venous sinus of the rat dura mater and the artery of the rat carotid body. In addition, we confirmed that both peptides are extracellularly released from the WP bodies into both vascular lumen and subendothelial layr by exocytosis in a manner of regulated pathway.It is widely accepted that EP-1 induces vasoconstriction mediated from ETA receptors on the sarcolemma of medial muscle cells in a manner of paracrine, and vasodilatation mediated from ETB receptors on the plasmalemma of endothelial cells in a manner of autocrine. The present immunocytochemisty showed that immunoreactivities of the ETB receptors are localized to the plasmalemma of endothelial cells of the transverse venous sinus and the artery in the carotid body, and that those of ETA receptors are localized to the sarcolemma of medial muscle cells of the transverse venous sinus. In the arterial system of the carotid body, we could not detect out immunoreactions of the ETA receptors. These findings suggest that ET-1 regulates the blood flow in the transverse sinus by inducing both vasocontraction mediated from ETA receptors and vasodilatation mediated from ETB receptors, and that ET-1 preserves an abundance of the blood flow through the carotid body by evoking the vasodilatation mediated from ETB receptors.